Aromatic polycarbonates belong to the group of industrial thermoplastics. They are distinguished by combination of the technologically important properties of transparency, heat distortion resistance and toughness.
To obtain high molecular weight polycarbonates by the phase interface process, the alkali metal salts of aromatic dihydroxy compounds (herein referred to as bisphenols) are reacted with phosgene in the two-phase mixture. The molecular weight may be controlled by the amount of monophenols, such as e.g. phenol or tert-butylphenol. Practically exclusively linear polymers are formed in these reactions. This may be demonstrated by end group analysis. By targeted use of so-called branching agents, as a rule polyhydroxylated compounds, branched polycarbonates are also obtained in this context.
For the preparation of polycarbonates by the phase interface process, reference may be made by way of example to H. Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, vol. 9, Interscience Publishers, New York 1964 p. 33 et seq. and to Polymer Reviews, vol. 10, “Condensation Polymers by Interfacial and Solution Methods”, Paul W. Morgan, Interscience Publishers, New York 1965, chap. VIII, p. 325.
For the preparation of polycarbonates by the melt transesterification process, the bisphenols are reacted in the melt with diaryl carbonates, usually diphenyl carbonate, in the presence of catalysts, such as alkali metal salts or ammonium or phosphonium compounds.
The melt transesterification process is described, for example, in the Encyclopedia of Polymer Science, vol. 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, vol. 9, John Wiley and Sons, Inc. (1964) and DE-C 10 31 512.
Polycarbonates based on 2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidines as monomers, which may be prepared by synthesis from phenolphthalein and an aniline hydrochloride derivative in aniline, are known from EP-A 1 582 549. This preparation is very involved and does not proceed satisfactorily. This bisphenol class thus has the industrial disadvantage of being accessible in only a very cumbersome manner.
However, due to their lack of adhesion to metals, the polycarbonates and copolycarbonates already described in the prior art have the disadvantage that they may have only a limited suitability or a suitability which is not optimum for use as a metallized component in e.g. high temperature uses.